Temperature regulated multiple burner supply system



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Aug. 11, 1959 E. o. ENGELS 2,899,135

TEMPERATURE REGULATED MULTIPLE BURNER SUPPLY SYSTEM Filed July 10, 1953 2 Sheets-Sheet 1 ,4 TTORNEYS.

g- 11, 1959 E. ENGELS 2,899,135

TEMPERATURE REGULATED MULTIPLE BURNER SUPPLY SYSTEM Filed July 10, 1953 2 Sheets-Sheet 2 A E34 27 INVENTOR.

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. fiTTORNEYS United States Patent TENIPERATURE REGULATED MULTIPLE BURNER SUPPLY SYSTEM Eugene 0. Engels, Saginaw, Mich, assignor to Baker Perkins, Inc., Saginaw, Mich.

Application July '10, 1953, Serial No. 367,322

12 Claims. (Cl. 236-15) [his invention relates to automatically regulated fuel supply systems, and more particularly to a regulatory system for adjusting the flow of fuel mixture to an oven manifold in accordance with the existent pressure in the manifold as well as in accordance with the heat requirements of the oven.

Conventional systems for supplying combustible mixture to the heating units of ovens and the like commonly regulate the volume of the fuel mixture supplied in accordance with the varying heat requirements of the ovens. Means responsive to the calorific demands of the oven operate to restrict the ports or orifices of conventional line control valves to decrease the flow of the gaseous fuel constituents if the temperature in the oven rises above the set temperature and conversely permit an increased flow through the orifices of the control valves when the temperature of the oven falls below the temperature for which the oven has been set. Ordinarily, mechanical stops are employed at these control valves to insure the flow of a minimum supply of combustible mixture at least sufficient to keep the burner or burners operating to insure that non-combusted gaseous fuel does not escape when the oven is operating at low temperatures. While such a system is quite satisfactory when but one burner is supplied by the oven manifold, it has definite and decided disadvantages when a plurality of burners are employed to heat the oven. I have particular reference to commercial baking ovens wherein it is the usual practice to provide a number of elongated, small capacity burners of the so-called strip or ribbon type to obtain a uniform heat distribution. f conventional mechanical stops of the type described are employed to insure the flow of a minimum supply of combustible mixture to the manifold, the heating range of the oven is necessarily limited, since the total minimum volume of mixture supplied must be sufficient to keep each burner burning with a minimum flame. Obviously, the calorific output of such an oven could not be decreased by the simple expedient of turning off some of the burners, since a greater amount of gas would merely be burned by the burners which remain on.

Further, in the initial firing of the oven, it is a desirable and safe practice to light each burner individually and observe that it is burning properly before lighting the next burner. It is evident that if only one or a few burners are turned on in conventional systems when the oven is demanding a maximum flow of fuel, the manifold pressure will be much greater than if all the burners were turned on simultaneously, and it will be exceedingly dilficult if not impossible to light the first and immediately succeeding burners due to the tendency of the flames to blow off.

One of the prime objects of the instant invention is to provide a regulatory system which controls the fuel flow in accordance with the manifold pressure as well as in accordance with the calorific demands of the oven and thus eliminates the necessity of providing mechanical stops in the control valves of the constituent supply lines and the disadvantages which accrue therefrom. Such a system will permit the manifold pressure to correspond to low heat demands of the oven regardless of the number of burners which are in operation and will permit the oven to be operated at lower temperatures.

Another object of the invention is to provide a regulatory system of the type described which enables a commercial baking oven to be operated over a wider range of temperatures so that the same oven which operates at relatively low temperatures to partially process rolls of the type which are frozen and thence finish-baked in the home by the purchaser, can be used to finish-bake bread, rolls and the like.

A further object of the invention is to provide a regulated fuel supply system which permits the conservation of fuel by allowing the oven to be operated at lower idling temperatures.

A still further object of the invention is to provide a regulatory system of the type described of simple and practical design, which is economical to install and requires very little maintenance.

Another object of the instant invention is to provide a regulatory system for supplying fuel to the burners of an oven which will maintain a stabilized manifold pressure which corresponds to the heating demands of the oven while controlling the pressure regardless of the number of burners which are operating, so that maximum pressures are not exceeded at the individual burners, and burners can be safely turned on or off.

A further object of the invention is to provide a regulatory fuel system for ovens in which manifold pressures are controlled in a manner to permit the simple and easy lighting of the burners.

With the above and other objects in view, the present invention consists in the combination and arrangement of parts, hereinafter more fully described, illustrated in the accompanying drawings, and more particularly pointed out in the appended claims, it being understood that changes may be made in the form, size, proportion, and minor details of construction, without departing from the spirit, or sacrificing any of the advantages of the invention.

In the drawings:

Fig. 1 is a schematic view of the various component elements of my regulatory system.

Fig. 2 is a side elevational View of the pressure stabilizer employed therein.

Fig. 3 is a schematic, sectional, elevational view of the throttler controller employed therein.

Fig. 4 is a sectional, rear elevational view of the relay employed in conjunction with the air controller.

Fig. 5 is a fragmentary, elevational view of the linkage for actuating the joint supply line valve, taken on the line 5'5 of Fig. 1.

Referring now more particularly to the accompanying drawings in which I have shown the preferred embodiment of my invention, the fuel gas and air lines which supply the burner manifold or header 10 are indicated at 11 and 12 respectively in Fig. 1. A valve assembly 13 is interposed in the lines 11 and 12 to control the flow of the fuel gas and air which are supplied at relatively low pressures, a valve 14 regulating the flow through the line 11 and a valve 15 controlling the flow through the line 12, The valves 14 and 15 which are connected by a stem or shaft 16 are provided with orifices or ports 17 and 18 respectively which are adjusted relative to the lines 11 and 12 on rotation of the stem 16 to regulate the flow therethrough. The stem 16 is actuated by a regulator system in accordance with the heat demands of an oven (not shown), and the pressure in the manifold 10in a manner which will be presently described. The lines 11 and 12 are joined as shown at a mixing T 19 which leads i .2,s99,1s V A a to the oven manifold 10. A plurality of elongated burners 20, of the ribbon type which are commonly employed in commercial baking ovens, are connected to the manifold by the lines 21, and burner cocks 22 are provided for each burner as usual to permit the burner be turned on and off.

The flow of gaseous mixture to the manifold is adjusted with relation to the variable demand of the oven by means including a throttler controller 23 which is provided to interpret the heat requirements of the oven and vary the pressure of a control fluid entering the controller 23 through a line 24. This fluid which is supplied from a convenient source (not shown) is preferably air supplied at a relatively high pressure to provide a wide range of control. By a relatively high pressure is meant a pressure which is measured in pounds per square inch instead of fractions of a pound per square inch or inches of water which constitutes a relatively low pressure.

The controller 23 is provided with a primary element which takes the form of a temperature sensitive bulb 25 located within the oven casing (not shown). The bulb 25 which is connected to a gas-filled capillary tube 26, transfers heat to a Bourdon-type spiral tube of elliptical cross section 27 which expands or contracts in overall diameter with changes in oven temperature. When the pressure within the spiral tube 27 is increased by an increased temperature within the oven, the spiral tube tends to straighten out and when the pressure within the tube 27 is decreased, the tube tends to curl up. This movement can be transferred to linkage which may be schematically depicted as a lever 28 on which is provided a flapper 29 for closing the nozzle 30 of a bleeder tube 31.

Flexible tubing 32 connects the line 24 and a tube 33 which has a calibrated orifice 34 opening into an enlarged end of the tube 31. Flexible tubing 35 on an extension 36 of the tube 31 adjacent the orifice 34 is connected to the line 37 which leads out of the air controller 23 to a pressure stabilizer or governor S. It will be obvious that the pressure of the air in the line 37 will depend on the amount of air which is permitted to bleed out of the nozzle 30, since the air is supplied at a constant pressure. The flapper 29 which is normally positioned a suflicient distance from the mouth of the nozzle 30 to maintain the oven at a given temperature by permitting a certain portion of the air to bleed off, moves toward the nozzle when the spiral tube 27 contracts, and further away from the nozzle upon a diametral expansion of the spiral tube 37. In the instant schematic representation, the bleeder tube 31 is depicted as being pivoted as at 38 relative to the scale 39 which is calibrated in degrees of temperature. The tube can be positioned relative thereto by set means (not shown), the position of the tube 31 being set with relation to the oven temperature desired. In this manner, the pressure of the control air admitted to the stabilizer S is varied according to the heat requirements of the oven. When the burners are first lit, the coil 27 will, of course, maintain the flapper 29 in substantially closed position, so that maximum pressures are provided in the line 37 until the oven nears the set temperature.

The pressure stabilizer S, which is shown in detail in Fig. 2, includes a pair of dish shaped casings 40 and 41 between which is fixed a diaphragm 42 carrying a centrally disposed, tubular stem 43. The manifold pressure is admitted to the lower chamber 44 thus formed through a passage 45, a line 46 connecting the manifold 10 and passage 45 as shown. The upper chamber 47 is maintained at atmospheric pressure, a passage 47a leading to atmosphere from the chamber 47 as shown. Since the pressure in the manifold is necessarily relatively low, being measured in inches of water, while the pressure of the air admitted from the line 37 is of sufiicient magnitude to be measured in pounds per square inch, I have provided a diaphragm system which wlil impose a differential pressure in opposition to the manifold pressure acting on the diaphragm 42. These forces can be applied so that the variable air pressure supplied by the control instrument 23 just balances the manifold pressure when the pressure in the manifold is in proper proportion to the pressure in the line 37.

The upper casing or cover 41 is provided with a central opening 48 through which the stem 43 extends and a spacer ring 49 is mounted on the casing 41 as shown. An intermediate diaphragm 50 is fixed between the casing 41 and spacer 49 and of course is connected centrally to the stem 43. A second spacer ring 52 is secured on the ring 49, and another diaphragm 53 is mounted therebetween and is similarly rigidly connected to the control stem 43. It is to be observed that the spacer 49 is interiorly shouldered or flanged as at 54, and that the ring 52 extends to the edge thereof, so that the effective area of the uppermost diaphragm 53 is less than the effective area of the intermediate diaphragm 50. The relatively high pressure air entering the compartment 55 between the diaphragms 50 and 53 through a passage 56 communicating with the line 37 is thus differentially imposed upon the stem 43. A nut 57 is provided on the reduced upper end of the hollow stem 43, and an adjusting screw 58 is mounted therein to adjust the stroke of the stem 43. The movement of the stem 43 is transmitted to an air relay assembly 59 which is supported on a bracket 60 provided on the ring plate 52. The assembly 59 comprises a housing 61 in which is a shaft 62, the lower reduced end 63 of the shaft extending out the reduced lower end of the housing 61, as shown, to be engaged by the screw 58. Air from a branch line 64 of the control fluid line 24, which has by-passed the air controller and is at the relatively high pressure of the supply source is permitted to enter the interior of the relay through a passage 65 when the oven demands more heat and thence proceeds through a line 66 to operate an air motor 67. Movement of the stem 62 and an arm 68 thereon toward the stabilizer S upon an increase in the pressure in the line 37 moves the valve 69 from its seat 69a to permit air in the valve chamber 70 to enter the interior of the relay 59. A spring 71 normally retains the valve 69 in closed position so that when the oven is operating at the set temperature and the system is balanced, the supply of air in the line 64 is prevented from entering the relay.

The air in the interior of the relay housing can be bled out a vent 72 when a valve 73 normally retained in closed position by a spring 74 is raised from its seat 73a by an arm 75 on the shaft 62 on movement of the shaft 62 in a direction away from the stabilizer S. When the system is in balance, the valve chamber 76, of course, is closed to the interior of the relay. A spring 77 in a cap housing 77a biases the shaft 62 in a direction toward the stabilizer S, and adjusting nut 78 closing the cap 77a to enable the pre-loading of the spring as desired.

The air motor assembly 67 comprises a bellows 79 having a central stem 80 fixed to a plate 81 provided in the end thereof, a spring 82 opposing contraction of the bellows 79 as shown. The projecting end of the stem 80 may be pivotally connected as at 83 to one end of a bell crank lever 84 which is pivotally mounted as at 85 on a fixed bracket 86. A rod 87 extending laterally from the opposite end of the bell crank lever 84 is secured to the outer end of a lever 88 which is rigidly connected to the valve stem 16. Clearly, axial movement of the bellows stem operates through this or linkage of other suitable design to rotate the valves 14 and 15 on the stem 16 and adjust the position of the ports 17 and 18 relative to the lines 11 and 12 to control the flow of the gas and air to the manifold 10.

The maximum amount of air which can pass to the air motor 67 and therefore the maximum pressure which can be obtained in the manifold 10 can be limited by adjusting the position of the adjusting screw 58, while the minimum supply of gaseous mixture which should flow to the manifold can be set by adjusting the nut 78.

The minimum pressure obtainable once the adjusting screw 58 and nut 77 have been set, will not be afiected by the number of burners which are turned on or off, and when the oven is operated at an idling temperature, most of the burners can be turned off to conserve fuel.

Under normal conditions, when the oven is operating at substantially the set temperature with all the burners 20 on, the pressure maintained in the manifold corresponds to the heat demand of the oven and remains substantially constant. If an increased load decreases the oven temperature below the set temperature at which it is to operate, the flapper 29 is moved toward the nozzle 30 of the bleeder tube 31. The pressure of the air entering the stabilizer S is thereupon increased with the result that the stem 43 is retracted, and the stem 62 in the air relay is permitted to move toward the stabilizer S and open the valve 69. The pressure of the air in the line 66 leading to the air motor 67 is thus increased, which moves the stem 80 outwardly against the action of the spring 82 to adjust the common stem 16 of the valves 17 and 18 and increase the flow of gas and air to the manifold 10. An increased flow of mixture to the manifold will raise the pressure therein and oppose the effect of the pressure entering the stabilizer from the controller with .the result that an equilibrant condition is once more soon established. Conversely, if the oven temperature increases beyond the set temperature, the flapper 29 is moved away from the nozzle 30 to permit the escape of all the controlled air which bleeds the air relay 59 and permits expansion of the bellows 79 in the air motor 67 to further restrict the lines 11 and 12 by adjusting the position of the valves 17 and 18.

If it is desired to operate the oven at extremely low temperatures or to idle the oven, a number of the burners 20 can be turned off and the oven will operate at the low manifold pressure prescribed by the low set temperature, regardless of the number of burners turned on or off. The minimum temperature at which the oven can operate will be determined by the calorific output of one burner operating with a minimum supply of fuel rather than of all the burners operating with a minimum supply of fuel as previously.

The burners of an oven which is provided with my new and improved regulatory system can be lit individually without danger when the oven is cold. In this instance, although the controller 23 would be admitting the full control pressure between the diaphragms 50 and 53 when the first burner is turned on, the manifold pressure would drop, which would lower the pressure in the compartment 44 and oppose the elfect of the full control pressure. This would temper the action of the control stem in the air relay and adjust the valves 17 and 13 until an equilibrium was established at a manifold pressure of a magnitude to operate only one burner at maximum pressure. When the second burner is tulned on, the manifold pressure would drop again and tend to oppose the action of the full control pressure until an equilibrant condition was again established at a burner pressure sufiicient only to operate two burners with maximum flames. This action would continue until all of the burners were lit, whence all burners would operate with maximum flames until the temperature for which the oven was set Was nearly reached at which point the control pressure and manifold pressure would level off to pressures sufiicient to maintain the set temperature.

When the oven is operating at a predetermined temperature with all of its burners on and it is desired to turn the oven off, the burners are likewise turned off in individual succession and the tendency, when the first and succeeding burners are turned off, is to momentarily increase the pressure in the manifold, thus bleeding air from the air motor 67 and relay 59 out the vent 72 and decreasing the flow of gaseous mixture to the manifold. The temperature at which the oven is to operate having been set back to zero, the control air entering the d .chamber 55 from the controller 23, would have no pressure, and this condition would maintain the stems 43 .and 62 in outward position to bleed all the air from the air motor, save that required to supply the predetermined minimum of fuel, and permit the spring 82 to almost close the ports 17 and 18.

It will thus be apparent that I have perfected a regulatory system of practical and efiicient design which widens the range of temperatures at which ovens of this type can be operated and perm-its them to be more safely and economically operated. The drawings and descriptive matter are in all cases to be interpreted as merely illustrating the invention rather than limiting the scope of the appended claims. For example, when the terms pressure compensating regulatory means, regulating means, and a pressure stabilizer assembly are employed in the claims, the means or assembly may include the relay 59 and means associated therewith for controllingthe valves 17 and 18 as well. When means for transmitting the resultant of the fuel pressure and control pressure are defined as connected to the fuel line valve means, the term means may mean the entire stabilizer and relay assembly. The terms stem and stem means may mean both the member 43 and member 62 in the various claims.

it is to be understood that various changes in the design of the component elements of the system may be made without departing from the spirit of the invention or the scope of the appended claims. For example, it is contemplated that a portion of the diaphragm means could :be mounted on the relay stem 62 in an equivalent combination. Further, the burners could be arranged in pairs or other groupings and cooks could turn pairs of burners oflf or on individually or the like.

What I claim is:

1. In a regulatory system for controlling the flow of a combustible fuel mixture to a header line which supplies the fuel mixture at a relatively low pressure to a plurality of oven burners, valve means operable to adjust the flow through said line, a pressure medium under a relatively high pressure, means for varying the pressure medium in accordance with the heat demands of the oven, a pressure stabilizer including a diaphragm carrying a central stem, a line leading from the header to impose the pressure therein on said diaphragm, said stabilizer also including a pair of diaphragms of different area connected to said stem, the diaphragm in said pair of larger area being adjacent to said first-mentioned diaphragm, port means admitting said pressure medium between said pair of diaphragms to differentially impose the pressure thereof on said stem in opposition to the pressure in said manifold, and means actuated by said stem for adjusting said valve means.

2. In a regulatory system for controlling the flow of a combustible fuel mixture to a header line which supplies a fuel mixture at a relatively low pressure to a plurality of oven burners, a line for supplying air at a relatively high pressure, controller means for modulating the air pressure in accordance with the heat requirements of the oven, a pressure stabilizer including a diaphragm and a stem, a line connecting said header and stabilizer to impose the pressure of the fuel mixture on one side of said diaphragm, said stabilizer including also a pair of spaced diaphragms of different area connected to said stem on the side of said first-mentioned diaphragm opposite the line leading from said header, an air line leading from said controller means to the chamber formed between the pair of diaphragms to impose the controlled pressure differentially in opposition to the header pressure, an air motor including a plunger, resilient means opposing movement thereof, a fuel supply line, valve means in the fuel supply line operable on movement of said plunger to adjust the flow of fuel mixture to said header, a relay having a stem in axial alignment with the stem of said stabilizer, a line for supplying air at a relatively high pressure to said relay, and a line connecting said relay and air motor, said relay having valve means connected to the line for supplying air to said relay closed to the line leading to said air motor when the relay stem is in normal position, and valve means venting the relay and air motor when said relay stem is moved to another position by said stabilizer stem to vary the pressure of the air operating said air motor.

3. In a regulatory system for controlling the flow of a combustible fuel mixture to a manifold which supplies the fuel mixture to a plurality of oven burners at a relatively low pressure, a fuel delivery line of said manifold, valve means adjustable to restrict the flow of said fuel mixture to said manifold, temperature sensitive means in the oven, a line for supplying control air at a relatively high pressure, modulating pressure controller associated with said temperature sensitive means to vary the pressure of the control air according to the heat demands of the oven, a pressure stabilizer, lines leading from said manifold to said stabilizer and from said controller to said stabilizer, said stabilizer including a stern and diaphragms connected thereto upon which the controlled pressure of said air and the pressure of the fuel mixture in said manifold act in opposition, an air relay having a stem substantially in axial alignment with the stem of said stabilizer, means for delivering air at a relatively high pressure to said relay, an air motor including a spring-retracted plunger, a line connecting said relay and air motor to impose the pressure of the air in said relay on said plunger and control its position, said air relay including vent means and having valves normally closing said delivery line and vent means, means carried by said air relay stem for operating said valves, and linkage connecting said valve means and said plunger to adjust the flow of fuel mixture in accordance with the position of said plunger.

4. The combination defined in claim 3 in which adjustable spring means is provided to oppose outward movement of said relay stem to urge said stem toward said stabilizer and permit setting of a minimum manifold pressure at which the system can be operated, and an adjusting screw provided on said stabilizer stem in engagement with said relay stem to permit setting of the maximum manifold pressure at which the system can be operated.

5. In a regulatory system for controlling the flow of a combustible fuel to a header which supplies the same at a relatively low pressure to a plurality of oven burners which can be individually turned on and off, a control fluid line, a pressure fluid therein at a relatively high pressure, controller means for modulating the pressure of said fluid in accordance with the heat requirements of the oven, a pressure stabilizer assembly, said assembly including a juxtaposed pressure stabilizer and fluid pressure relay, axially movable central stem means for said assembly, spaced-apart diaphragms of diflerent area on said stem means, a line connecting said header and stabilizer assembly adjacent the side of the diaphragm of larger area remote from the smaller diaphragm to impose the relatively low pressure of the fuel in the header on said larger diaphragm, a fuel delivery line leading to said header, a line leading from said controller to the side of said smaller diaphragm remote from the larger diaphragm to impose the relatively higher controlled pressure of said fluid in opposition to the pressure of the fuel in the header, valve means in the fuel line operable to adjust the flow of fuel therethrough, a pressure fluid line leading from said assembly, pressure fluid therein, means operated thereby to adjust said valve means, and means in said relay for varying the fluid pressure in the said line leading from said assembly in response to the movement of said stem means to control the operation of said valve means in accordance with both the heat requirements of the oven and the pressure in the header.

6. The combination defined in claim 5 in which said stem means comprises a pair of juxtaposed, aligned, axially movable stems in engagement, one of which is in the stabilizer and the other in the relay, one of said stems being adjustable toward and away from the other.

7. In a regulatory system for controlling the flow of a combustible fuel to a header which supplies the same at a relatively low pressure to a plurality of oven burners which can be individually turned on and 01f, a control fluid line, a pressure fluid therein at a relatively high pressure, controller means for modulating the pressure of said fluid in accordance with the heat requirements of the oven a pressure stabilizer assembly, said assembly including a. juxtaposed pressure stabilizer and pressure fluid relay, axially movable central stem means for said assembly, spaced-apart diaphragms of different area on said stem means, a line connecting said header and stabilizer adjacent the side of the diaphragm of larger area remote from the smaller diaphragm to impose the relatively loW pressure of the fuel in the header on said larger diaphragm, a fuel delivery line leading to said header, a line leading from said controller to the side of said smaller diaphragm remote from the larger diaphragm to impose the relatively higher controlled pressure of said fluid in opposition to the pressure of the fuel in the header, valve means in the fuel line operable to adjust the flow of fuel therethrough, a line for supplying a pressure fluid to said relay, pressure fluid therein at a relatively high pressure, a pressure fluid motor controlling said valve means, a line connecting said relay and fluid motor, said relay having valve means connected to the line for supplying pressure fluid to said relay closed to the line leading to said motor when the stem means is in normal position, and valve means venting the relay and line to said motor when said stem means is moved to another position to vary the pressure of the fluid operating said fluid motor.

8. In a regulated fuel supply and heating system for ovens, an oven manifold, a plurality of burners supplied by said manifold, at least certain of said burners having means associated therewith for turning the same off and on without turning off or on other of the burners, a fuel delivery line connected to said manifold, a combustible fuel in said line, valve means operable to control the flow of fuel through said line, a control fluid line, a pressure medium in said line, modulating means settable according to the temperature at which the oven is to operate associated with said control fluid line to vary the pressure of said medium according to the relation of the actual temperature in the oven to the temperature at which it is to operate, a pressure stabilizer and pressure fluid relay assembly, said assembly including a juxtaposed pressure stabilizer and pressure fluid relay, axially movable stem means for said assembly, diaphragm means thereon, lines leading to said assembly from said manifold and said controller means and imposing the pressures in the manifold and line leading from the controller on said diaphragm means in opposite directions, a pressure fluid line leading from said assembly, pressure fluid therein, means operated by the pressure fluid in said latter line for operating said valve means, and means in said relay for varying the fluid pressure in the said line leading from said assembly in accordance with the movement of said stem means and the resultant of the pressures applied oppositely to said diaphragm means which controls the same.

9. A fuel supply and heating system for ovens comprising, an oven manifold, burners connected thereto, said burners having means for turning the same off and on individually, a delivery line leading to said manifold, a combustible fuel mixture carried by said line, valve means operable to control the flow of said mixture through said line, a control fluid line, a pressure medium in said line, controller means responsive to temperature changes in the oven varying the pressure medium in the control line according to the heat requirements of the oven, a pressure stabilizer assembly, said assembly including a juxtaposed pressure stabilizer and pressure fluid relay, axially movable stem means for said assembly, said stem means comprising an axial-ly movable stem in said stabilizer and an axially aligned, axially movable stern in said relay, diaphragm means on said stem means, lines leading to said assembly from said manifold and controller means and entering the same at spaced points on opposite sides of said diaphragm means to impose the pressures in the manifold and line leading from the controller in opposition, means for delivering pressure fluid at a relatively high pressure to said relay, a pressure fluid motor including a plunger, a line connecting said relay and motor to impose the pressure of the air in said relay on said plunger and control its position, said relay including vent means and having valves normally closing said pressure fluid delivery line and vent means, means on said relay stem opening said valves when said stern means is moved by said diaphragm means, and linkage connecting said valve means and said plunger to adjust the flow of fuel mixture in accordance with the position of said plunger.

10. In a regulatory system for controlling the flow of a combustible fuel to a header which supplies the same at a relatively low pressure to a plurality of oven burners, the flow through at least one of said burners being adjustable relative to the flow through the other burners, a control fluid line, a pressure fluid therein at a relatively high pressure, controller means for modulating the pressure of said fluid in accordance with the heat requirements of the oven, a pressure stabilizer assembly, said assembly including a pressure stabilizer and fluid pressure relay, stem means for said assembly, spaced apart diaphragrns of different area on said stem means, a line connecting said header and stabilizer adjacent the side of the diaphragm of larger area remote from the smaller diaphragm to impose the relatively low pressure of the fuel in the header on said larger diaphragm, a fuel line leading to said header, a line leading from said controller to the side of said smaller diaphragm remote from the larger diaphragm to impose the relatively higher controlled pressure of said fluid in opposition to the pressure of the fuel in the header, flow control means in the fuel line operable to adjust the flow of fuel therethrough, a pressure fluid line leading from said assembly, pressure fluid therein for operating said flow control means, and means in said relay for varying the fluid pressure in the said line leading from the assembly in response to the movement of said stem means to control the operation of said flow control means in the fuel line in accordance with both the heat requirements of the oven and the pressure in the header.

11. In a regulated fuel supply system for an oven; a header line with a fluid fuel under a pressure normally measured in inches of water; a plurality of burners connected thereto of which at least one may be adjusted to admit less fuel than the others; a fluid pressure operated fuel delivery control means operable to control the delivery of fuel through the header line; a first control fluid line with a control fluid medium under a pressure normally measured in pounds per square inch; modulating means varying the pressure in said first control line in accordance with the heat requirements of the oven; a second control fluid line with a control fluid for operating said fuel delivery control means connected thereto; means connected with said header line and first control fluid line receiving the relatively high pressure of the control line and the relatively low pressure of the header line in opposition and compensating for the dilference in force exerted by the low pressure fuel in the header line and the high pressure fluid in the first control fluid line; said means including a pressure responsive means of large elfective area receiving the low pressure force of the header line connected with a pressure responsive means of smaller effective area receiving the relatively high pressure of the first control fluid line; and means varying the pressure in the second control fluid line in accordance with the resultant of the forces imposed on the members of different effective area to operate said fuel delivery control means in accordance with the pressure in the manifold line and the pressure in said first control fluid line.

12. In an oven fuel supply system; a header line for a fluid fuel under a pressure normally measured in inches of Water; a plurality of burners connected thereto of which at least one may be adjusted to admit less fuel than the others; a fluid pressure operated fuel delivery control means operable to control the delivery of fuel through the header line; a first control fluid line for a control fluid medium under a pressure normally measured in pounds per square inch; means settable according to the temperature at which the oven is to operate varying the pressure in said first control line in accordance with the relation of the actual temperature of the oven to the set temperature at which it is to operate; a second control fluid line for a control fluid for operating said fuel delivery control means connected thereto; proportioning means connected with said header line and first control fluid line receiving the relatively high pressure of the control line and the relatively low pressure of the header line in opposition and compensating for the difference in force exerted by the low pressure fuel in the header line and the high pressure fluid in the first control fluid line; said proportioning means including means for transmitting the resultant of said low and high pressures connected with a pressure controlled member of large effective area and a pressure controlled member of small effective area; and means controlling the pressure in the second fluid line in accordance with the resultant of the forces imposed on the members of different eifective area to operate said fuel delivery control means in accordance with the pressure in the manifold line and the pressure in said first control fluid line.

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